Meeting Abstract
The time interval between successive eggs in a clutch has been known to vary substantially among species; many species lay at a rate of one egg per day while some wait up to 30 days to lay the next egg in the clutch. For no species have time intervals of less than a day been observed between ovipositions. Our current understanding of avian physiology suggests that laying eggs at intervals shorter than 24h should be physiologically impossible, because ovulation and oviposition are timed according to the light/dark cycle, only a single ovarian follicle should be ready to ovulate on a given day, and more than one egg in the shell gland would likely lead to shell abnormalities. However based on anecdotal accounts of hens that routinely produce two fully formed eggs in one day (termed double ovipositions), we hypothesized that laying hens may exhibit this pattern more often than was previously realized. To test this, we observed a flock of laying hens, monitoring the time of oviposition for each hen on each day using a thermal camera. We found that 13% of hens produced a double oviposition, often producing a second egg within 2.5h of the first, at least once during the observation period. One hen produced double ovipositions multiple times, and one produced 3 eggs in a day. Further, we then monitored a second flock of laying hens and found additional evidence of double ovipositions. Eggs that were part of double ovipositions showed no external shell abnormalities and weighed the same as those that were single ovipositions, suggesting that laying hens can, and do, produce two fully formed eggs within hours of one another. This finding refutes our currently understanding of avian reproductive physiology and calls for additional work on the regulation of ovulation and oviposition, particularly in laying hens.
